Fundamental information on corrosion mechanisms will be derived from techniques in vivo as well as in vitro; linear polarization techniques will be correlated with potentiosynamic hysteresis and constand potential polarization techniques in vitro; the optical effects of tarnish will be measured by a tristimulus colorimeter over time. Metal specimens will be made of noble and precious metal casting alloys, base metal casting alloy and dental amalgams. The problems of tarnish and corrosion affect the dental profession and patients via structural weakening of the metal, optical discoloration, or toxic/hypersensitive reactions to the corrosion products. The recent increases in the cost of noble and precious metals has caused renewed interest in alternative products. Lower levels of precious metals introduce larger amounts of potentially corrodible elements, some combinations of which may corrode severely. Regulatory agencies have resorted to composition limits (high in noble or passivating elements) rather than performance standards because the appropriate tarnish and corrosion tests have not been tested in animals or humans, and they have not gained acceptance from workers in the field. Accelerated laboratory tests exist in the literature but have not been related to in vivo models. This research will attempt to develop methodology for acquisition of data on the in vivo tarnish and corrosion of dental restorative metals in human patients and then use this information to suggest methodology for laboratory test conditions which can simulate clinical performance.